Blender VSE - How can I just render the audio to do some editing to it?
Depending on how the video is encoded, you might be able to import video as a sound strip into the VSE.

Goto  Add -> Sound  and when the file selection screen opens, you will have to turn off file filtering.  (So you can select something more than 'sound' files.)



Then you can select a video file, and it will only import the sound.